power loss

frontend/test-support/random.ts

@@ -0,0 +1,25 @@
+/** A seed controls harness choices; production UUIDs and OS scheduling remain
+ * nondeterministic. The concrete action trace is the stronger replay artifact. */
+export class Random {
+    private state: number;
+    public constructor(seed: number) {
+        if (!Number.isInteger(seed) || seed < 0 || seed > 0xffffffff)
+            throw new Error("Seed must be a uint32");
+        this.state = seed;
+    }
+    public next(): number {
+        this.state = (this.state + 0x6d2b79f5) >>> 0;
+        let n = this.state;
+        n = Math.imul(n ^ (n >>> 15), n | 1);
+        n ^= n + Math.imul(n ^ (n >>> 7), n | 61);
+        return ((n ^ (n >>> 14)) >>> 0) / 4294967296;
+    }
+    public int(max: number): number {
+        if (!Number.isSafeInteger(max) || max < 1)
+            throw new Error("Empty random choice");
+        return Math.floor(this.next() * max);
+    }
+    public pick<T>(values: readonly T[]): T {
+        return values[this.int(values.length)];
+    }
+}